Motion Sensors

PIR Sensor

PIR, "Passive Infrared", "Pyroelectric", or "IR motion" sensors detect a change in temperature, possibly from a mammel. They are made of a pyroelectric sensor that detects infrared radiation.

Adafruit Learn PIR Sensor

SparkFun OpenPIR

The SparkFun OpenPIR s a highly customizable Passive Infrared (PIR) sensor. It has trimpots to adjust sensitivity (view distance) and to control the length of time the output signal remains HIGH, and a trigger that supports single-pulse and dual-pulse dection modes. Sparkfun Hookup Guide.

The digital output goes HIGH when motion is detected. An analog output provides more details about the motion detected. The digital output magnitude varies in proportion to the power input VCC (3.3V or 5.0 VDC).

When the sensor is first powered, the green LED will blink at 2 Hz indicating initialization (start-up sequencing). Initialization takes 90 seconds. During initialization, no digital output will occur in response to motion. When initialization is complete the green LED will turn off, and thereafter only turn on when motion is sensed.

My personal experience with this sensor is it provides more reliable mammal motion detection than the commonly used sensor sold by Adafruit PN 189, Parallax SKU 555-28027, and others.

IMPORTANT! You need to treat the digital output of the PIR sensor the same as you would for a pushbutton switch and implement a debounce timer.

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